feat: enhance Milkdown editor and file system functionality

- Normalize line endings in Markdown export for DOCX files.
- Improve selection serialization to Markdown with better handling of empty documents.
- Add a new `updateFile` function to the file system for updating file properties.
- Introduce video transcoding capabilities using FFmpeg, supporting various video formats.
- Update AGENTS.md for clearer plugin structure and responsibilities.
- Add scoped styles for TreeNodeItem component to improve UI consistency.
- Implement cross-origin isolation headers in Vite configuration for enhanced security.
- Remove obsolete test_cross.py file.

src/composables/useFileSystem.js

@@ -98,8 +98,12 @@ function isBinaryExtension(ext) {
 function inferMimeType(name, fallback = '') {
   const ext = getExtension(name)
   const map = {
+    avi: 'video/x-msvideo',
     md: 'text/markdown',
     markdown: 'text/markdown',
+    mkv: 'video/x-matroska',
+    mov: 'video/quicktime',
+    mp4: 'video/mp4',
     txt: 'text/plain',
     json: 'application/json',
     js: 'text/javascript',
@@ -126,11 +130,17 @@ function inferMimeType(name, fallback = '') {
     ps1: 'text/plain',
     jpg: 'image/jpeg',
     jpeg: 'image/jpeg',
+    flv: 'video/x-flv',
+    m4v: 'video/x-m4v',
     png: 'image/png',
     gif: 'image/gif',
     webp: 'image/webp',
     svg: 'image/svg+xml',
-    pdf: 'application/pdf'
+    pdf: 'application/pdf',
+    ogg: 'video/ogg',
+    ogv: 'video/ogg',
+    webm: 'video/webm',
+    wmv: 'video/x-ms-wmv'
   }
   return fallback || map[ext] || 'application/octet-stream'
 }
@@ -398,6 +408,43 @@ export function useFileSystem() {
     return true
   }
 
+  function updateFile(id, nextValue, options = {}) {
+    const file = records.value.find((item) => item.id === id && item.type === 'file')
+    if (!file) return false
+
+    const nextName = options.name || file.name
+    const isBlobValue = nextValue instanceof Blob
+    const nextContent = isBlobValue ? (options.content ?? '') : String(options.content ?? nextValue ?? '')
+    const nextSize = typeof options.size === 'number'
+      ? options.size
+      : isBlobValue
+        ? nextValue.size
+        : new Blob([nextContent]).size
+
+    if (nextSize > MAX_FILE_SIZE) {
+      error.value = '单个文件不能超过 1GB'
+      return false
+    }
+
+    file.name = nextName
+    file.updatedAt = Date.now()
+    file.mimeType = inferMimeType(nextName, options.mimeType || (isBlobValue ? nextValue.type : file.mimeType))
+    file.size = nextSize
+    file.storageKind = options.storageKind || (isBlobValue ? 'blob' : 'text')
+    file.content = nextContent
+    file.previewText = options.previewText ?? (file.storageKind === 'text' ? nextContent : '')
+    file.isTruncatedPreview = Boolean(options.isTruncatedPreview)
+    file.blob = isBlobValue ? nextValue : null
+    records.value = [...records.value]
+    error.value = null
+
+    persistRecord(file).catch(() => {
+      error.value = '保存文件失败，可能是浏览器存储空间不足'
+    })
+    touchParent(file.parentId)
+    return true
+  }
+
   function createFolder(parentId, name) {
     if (records.value.length >= MAX_NODES) {
       error.value = `目录项数量不能超过 ${MAX_NODES} 个`
@@ -594,8 +641,12 @@ export function useFileSystem() {
   function getFileIcon(name) {
     const ext = getExtension(name)
     const iconMap = {
+      avi: 'video',
       md: 'markdown',
       markdown: 'markdown',
+      mkv: 'video',
+      mov: 'video',
+      mp4: 'video',
       txt: 'text',
       json: 'json',
       js: 'javascript',
@@ -617,13 +668,19 @@ export function useFileSystem() {
       jpeg: 'image',
       png: 'image',
       gif: 'image',
+      flv: 'video',
+      m4v: 'video',
       webp: 'image',
       svg: 'image',
+      ogg: 'video',
+      ogv: 'video',
       pdf: 'pdf',
       doc: 'word',
       docx: 'word',
       ppt: 'ppt',
       pptx: 'ppt',
+      webm: 'video',
+      wmv: 'video',
       xls: 'excel',
       xlsx: 'excel',
       zip: 'zip'
@@ -681,6 +738,7 @@ export function useFileSystem() {
     stats,
     load,
     createFile,
+    updateFile,
     createFolder,
     rename,
     remove,